1. Field of the Invention
The present invention relates to a communication apparatus and more particularly to a communication apparatus which has an automatic communication function and effects communication through a telephone line.
2. Description of the Prior Art
A facsimile machine having an automatic communication function to automatically receive a text sent from a calling station or automatically send a text to a called station in response to a call signal from a calling station facsimile machine, has been known.
The facsimile machine having such an automatic communication function usually has a manual receive mode in which the call signal is received by a conventional telephone set and then the line is manually switched to the facsimile machine. The selection of the manual mode and the auto-mode is usually done by a switch mounted on a console panel of the facsimile machine.
In the manual receive mode, the telephone set associated with the facsimile machine may be used in the same manner as a conventional telephone sets and can receive a call even from a public telephone. However, an operator must intervene when a text is to be received. The operator must hook up a handset, depress a receive button and switch the line to the facsimile machine.
In the auto-receive mode, the facsimile machine can automatically receive the text sent from another facsimile machine but the telephone set connected to the facsimile machine has its speech function taken away and cannot receive a call from a public telephone. FIG. 1 illustrates an example. A receiver used is a G2/G3 facsimile machine which meets the CCITT Recommendation T3 and T4.
The facsimile machine in the auto-receive mode sends out a CED (Call Station Identification) signal 1 to a line for a call from a public telephone. Then, the called station facsimile machine sends out NSF (Non-Standard Facilities) signal 2, CSI (Called Subscriber Identification) signal 3 and DIS (Digital Identification Signal) signal 4 to the line. Then, the facsimile machine tries to receive NSS (Non-Standard Facilities Set-up) signal, TSI (Transmitting Subscriber Identification) signal and DCS (Digital Command Signal) signal from the sending station which correspond to the NSF CSI and DIS signals, respectively. However, since the NSS, TSI and DCS signals are not sent out of a conventional telephone set, the receiving station facsimile machine, after a three-second waiting period, sends out GI2 (Group Identification Group 2) signal 5, NSF signal 2, CSI signal 3 and DSI signal 4 to the line.
Then, the facsimile machine tries to receive GC2 signal, NSS signal, TSI signal and DCS signal from the sending station which correspond to GI2, NSF, CSI and DIS signals, respectively. However, since the GC2 (Group Command Group 2) signal, NSS signal, TSI signal and DCS signal are not sent out of the conventional telephone set, the receiving station facsimile machine, after a three-second waiting period, again sends out the GI2, NSF, CSI and DIS signals to the line. After repeating the above steps for 35 second, timed from the initial transmission of the NSF, CSI and DIS signals, the receiving facsimile machine determines an error and terminates the connection.
In an auto-send mode in which a preset input is sent to a destination station at a designated time, a significant protocol signal sent from the called station immediately after the call is detected. If the called station facsimile machine is in the manual-receive mode or the line is busy and the significant protocol signal is not detected, the call signal is resent after a predetermined period (e.g. one minute). The redialing is effected at least two times. If the called station facsimile machine is in the manual-receive mode, the operator will respond to the call but because the significant protocol signal is not detected, facsimile communication is not attained.
A user who has only one telephone line usually sets the telephone set to the conventional speech mode and does not set the facsimile machine to the auto-communication mode. Accordingly, the auto-communication function is not effectively used.
This problem is common to other communication apparatus having the auto-communication function such as a personal computer or word processor having a communication function.